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help / color / mirror / Atom feedFrom: Pavel Stehule <[email protected]>
To: Wolfgang Walther <[email protected]>
Cc: Dmitry Dolgov <[email protected]>
Cc: Laurenz Albe <[email protected]>
Cc: Erik Rijkers <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: DUVAL REMI <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: proposal: schema variables
Date: Sat, 16 Nov 2024 16:36:19 +0100
Message-ID: <CAFj8pRCeh3u9rSqq0me52iik9+pNUvYeb8OgbuFxJArrb4VDjA@mail.gmail.com> (raw)
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so 16. 11. 2024 v 15:56 odesÃlatel Wolfgang Walther <[email protected]>
napsal:
> Dmitry Dolgov:
> > This sounds to me like an argument against allowing name clashing between
> > variables and tables. It makes even more sense, since session variables
> are in
> > many ways similar to tables.
>
> +1
>
It doesn't help too much, because the unique tuple (schema, name), and
there is a search path.
Secondly, the pg_class is not good enough for description of scalar
variables, and enhancing pg_class for scalar variables can be messy.
>
> My mental model of a session variable is similar to a single-row,
> optionally global temporary, table.
>
> Is there any substantial difference that I am not aware of?
>
What I know, the variables are used as query parameters, not as relations -
Oracle, DB2, MSSQL, MySQL, ...
semantically, yes - it is a global temporary object, but it can be scalar
or composite value - it is not row.
(global (temp)) table can hold 0, 1 or more rows (and rows are always
composite of 0..n fields). The variable holds a value of some type.
Proposed session variables are like plpgsql variables (only with different
scope). In Postgres there is a difference between a scalar variable and
composite variable with one field.
Regards
Pavel
> Best,
>
> Wolfgang
>
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